Anti-Xa assays are seldom rapidly available, prompting clinicians to frequently administer four-factor-prothrombin complex concentrate (4F-PCC) empirically.

Determine if the thrombotic risk increases when preoperative factor Xa inhibitor (XaI) levels are low or unmeasured.

We analyzed retrospectively all patients who received 4F-PCC between September 2018 and July 2024 at five hospitals in the Hamilton region and screened for those with emergency surgery/invasive procedure as the main indication. The primary outcomes were symptomatic or asymptomatic, objectively verified arterial or venous thromboembolism within 7 days of 4F-PCC infusion. The secondary outcome was the same between postoperative days 8 and 30. XaI levels were determined with an anti-Xa assay, calibrated with the respective oral anticoagulant used by the patient.

Four-F-PCC at a median dose of 2,000 units (interquartile range, 2,000–2,000) was administered to 227 patients on apixaban (143; 63%), rivaroxaban (72; 32%), or edoxaban (12;5%). The mean age was 76 years, and 42% were female. Prophylaxis against venous thromboembolism was started promptly in 214 patients (94%) after a median of 1 day (interquartile range, 1–2). Thromboembolism within 7 days occurred in 1 of 38 patients (3%) with high XaI level, 0 of 24 with low level, and 9 of 165 (5%) with no level.

The risk of thromboembolism after 4F-PCC in patients on XaI and emergency surgery/invasive procedures appears to be similar among patients with preoperative XaI levels that are high, low, or not measured. This information might be helpful in settings where rapid anti-Xa testing is unavailable.

S.S. and M.P. presented the initial study idea. M.P. provided data from Transfusion Medicine. A.E. and N.I. performed the screening and data capture. S.S., with input from A.E., performed the analyses and wrote the manuscript. All authors read, revised, and approved the manuscript.

Received: 08 December 2025

Accepted after revision: 12 March 2026

Accepted Manuscript online:
17 March 2026

Article published online:
24 March 2026

© 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).

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